<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>变量-布尔类型</title>
</head>
<body>
    <script>
        var value1 = "123";
        var value2 = 0;
        var value3 = null;
        var value4;
        var value5 =true;
        var value6 = "a"-1;

        console.log(typeof(value1)); // string
        console.log(typeof(value2)); // number
        console.log(typeof(value3)); // object
        console.log(typeof(value4)); // undefined
        console.log(typeof(value5)); // boolean
        console.log(typeof(value6)); // number
        </script>
</body>
</html>